Influence of Pore Size on Carbon Dioxide Diffusion in Two Isoreticular Metal–Organic Frameworks
Why this work is in the frame
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Bibliographic record
Abstract
The rapid diffusion of molecules in porous materials is critical for numerous applications including separations, energy storage, sensing, and catalysis. A common strategy for tuning guest diffusion rates is to vary the material pore size, although detailed studies that isolate the effect of changing this particular variable are lacking. Here, we begin to address this challenge by measuring the diffusion of carbon dioxide in two isoreticular metal–organic frameworks featuring channels with different diameters, Zn 2 (dobdc) (dobdc 4– = 2,5-dioxidobenzene-1,4-dicarboxylate) and Zn 2 (dobpdc) (dobpdc 4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate), using pulsed field gradient NMR spectroscopy. An increase in the pore diameter from 15 Å in Zn 2 (dobdc) to 22 Å in Zn 2 (dobpdc) is accompanied by an increase in the self-diffusion of CO 2 by a factor of 4 to 6, depending on the gas pressure. Analysis of the diffusion anisotropy in Zn 2 (dobdc) reveals that the self-diffusion coefficient for motion of CO 2 along the framework channels is at least 10,000 times greater than for motion between the framework channels. Our findings should aid the design of improved porous materials for a range of applications where diffusion plays a critical role in determining performance.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.004 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it